CN107848059B

CN107848059B - Gas shielded arc welding method

Info

Publication number: CN107848059B
Application number: CN201680044307.9A
Authority: CN
Inventors: 宫田实; 铃木励一; 田中正显; 深堀贡; 小川贵史
Original assignee: Mazda Motor Corp; Kobe Steel Ltd
Current assignee: Mazda Motor Corp; Kobe Steel Ltd
Priority date: 2015-07-31
Filing date: 2016-07-27
Publication date: 2021-02-02
Anticipated expiration: 2036-07-27
Also published as: US10864594B2; DE112016003482T5; JP2017030016A; CN107848059A; WO2017022585A1; JP6795290B2; US20180221982A1; MX2018001250A

Abstract

The present invention relates to a gas shielded arc welding method for welding while supplying a consumable electrode with a shielding gas through a welding torch, wherein the welding torch includes a nozzle having an inner diameter of 15mm or more, a nozzle-base metal distance between a tip of the nozzle and a material to be welded is 22mm or less, and a ratio (inner diameter of the nozzle/nozzle-base metal distance) is 0.7 or more and 1.9 or less. This can improve the effect of shielding the atmosphere from the shielding gas, and can suppress oxidation of the bead surface after welding or oxidation at the time of atmosphere entry, and can reduce the amount of slag.

Description

Gas shielded arc welding method

Technical Field

The present invention relates to a gas-shielded arc welding method, and more particularly, to a gas-shielded arc welding method capable of suppressing an oxidation phenomenon of a weld surface and a projection of a weld bead shape due to oxygen in the atmosphere. Also disclosed are a welded article produced by the gas metal arc welding method and a method for producing the same.

Background

The shield gas for gas shielded arc welding generally functions to shield the arc, the molten metal, and the consumable electrode from the atmosphere and to prevent nitriding and oxidation of the molten portion. However, the shielding gas is disturbed by external factors such as wind and construction conditions such as the posture of the welding torch, and nitrogen in the atmosphere is mixed into the molten metal during welding. Welding defects such as pits and blowholes occur. Further, if oxygen in the atmosphere is mixed into the molten metal during welding, the bead shape becomes convex, and if the amount of oxygen in the molten metal increases, excessive slag is generated on the surface of the weld bead after welding.

In order to prevent such welding defects, weld bead projection, and slag, patent document 1 discloses a piercing member provided on the discharge port side of the nozzle as a function of blocking the atmosphere. By providing the perforated member, the flow of the shield gas can be rectified by the differential pressure, and the flow velocity distribution of the shield gas can be made more uniform.

Further, patent document 2 discloses that a straight portion Dp and a choke portion are provided in advance in a gas nozzle, and that the relationship between the inner diameter Do of the choke portion and the axial length L satisfies a predetermined value (1.5 ≦ Dp/Do ≦ 2.5, 1.0 ≦ L/Dp)). This describes that the weld zone can be well protected with the protective gas, and that inclusion of oxygen (O) and nitrogen (N) in the air can be suppressed, whereby a sound weld structure can be obtained.

[ Prior art documents ]

[ patent document ]

[ patent document 1] Japanese laid-open patent publication No. 2015-80807

[ patent document 2] Japanese laid-open patent application No. 2002-28785

Both patent document 1 and patent document 2 relate to a structure of a gas nozzle, and are intended to suppress entrainment of oxygen and nitrogen in the atmosphere from the viewpoint of gas flow.

However, these techniques do not consider the reaction with oxygen in the high-temperature portion of the molten metal, and are small-diameter nozzles. Therefore, the protection region is limited, and it is difficult to suppress the oxidation reaction of the high-temperature molten metal at the time of high-speed welding.

Further, as a countermeasure for involving in the atmosphere, there is a method of adding Al or Ti which easily reacts with nitrogen to the consumable electrode with respect to nitrogen in the atmosphere to form a nitride, thereby suppressing pits and pores. However, no method for suppressing the generation of slag by oxidation reaction caused by oxygen in the atmosphere has been reported so far.

In addition, in the conventional technique, even when the welding torch is protected directly below, the weld metal immediately after the welding torch passes through is still outside the protection range, and is exposed to the atmosphere. The weld metal immediately after the passing of the welding torch is already solidified, but the weld bead surface is at a high temperature, so that the reaction rate with oxygen in the atmosphere is high, and the slag is likely to be generated. This is a particularly significant problem in welding at a high welding speed.

Disclosure of Invention

In view of the above circumstances, the present invention provides a gas shielded arc welding method capable of suppressing oxidation of the bead surface immediately after welding or oxidation at the time of atmosphere entry while improving the shielding effect of the shielding gas against the atmosphere, and reducing the amount of slag.

As a result of extensive studies, the present inventors have found that the above-described problems can be solved by defining the inner diameter of the nozzle and achieving an appropriate nozzle-base material distance corresponding to the inner diameter, and have completed the present invention.

That is, the present invention relates to the following [1] to [10 ].

[1] A gas shielded arc welding method for performing welding while feeding a consumable electrode through a welding torch and flowing a shield gas,

the welding torch may comprise a nozzle that is,

the inner diameter of the nozzle is more than 15mm,

the distance between the tip of the nozzle and the welded material is 22mm or less, and the distance between the nozzle and the base material is smaller than

The ratio (inner diameter of the nozzle/distance between the nozzle and the base material) is 0.7 or more and 1.9 or less.

[2] The gas-shielded arc welding method according to the above [1], wherein a flow rate of the shielding gas is 18L/min or less.

[3] The gas-shielded arc welding method according to the above [1] or [2], wherein a ratio represented by (a flow rate of the shielding gas/an inner diameter of the nozzle) is 0.65L/min mm or more and 1.10L/min mm or less.

[4] The gas-shielded arc welding method according to any one of the above [1] to [3], wherein the shielding gas contains 92% or more of Ar, and the balance is at least one of carbon dioxide and oxygen, and unavoidable impurities.

[5] The gas-shielded arc welding method according to any one of the above [1] to [4], wherein the consumable electrode contains S at 0.015 mass% or more with respect to a total mass.

[6] The gas-shielded arc welding method according to any one of the above [1] to [5], wherein the average welding current is 250A or less.

[7] The gas-shielded arc welding method according to any one of the above [1] to [6], wherein the pulse current control is performed such that the peak current is 380A or more and 530A or less and the peak width is 0.5 to 2.0 milliseconds.

[8]According to the above [1]]～[7]The gas-shielded arc welding method of any one of the above aspects, wherein the material to be welded has a coating amount of 20 to 100g/m²The galvanized steel sheet according to (1).

[9] A method for producing a welded article, comprising a step of welding by the gas metal arc welding method according to any one of the above [1] to [8 ].

[10] A welded article welded by the gas-shielded arc welding method according to any one of the above [1] to [8 ].

According to the present invention, by defining the inner diameter of the nozzle of the welding torch and setting an appropriate nozzle-base metal distance corresponding to the inner diameter, the entrainment of the atmosphere can be suppressed, and the amount of oxygen and nitrogen in the molten metal can be kept low. Therefore, it is possible to suppress the formation of blowholes due to nitrogen, the formation of projections in the shape of the weld bead due to oxygen, and the increase in the amount of slag.

Further, when a predetermined amount of sulfur (S) is contained in the consumable electrode (hereinafter referred to as "wire"), S is preferentially surface-adsorbed in the molten pool immediately below the arc, so that oxidation reaction at the time of rolling up the bead surface or the atmosphere immediately after welding can be suppressed, and slag generated on the bead surface after welding can be further suppressed.

Drawings

Fig. 1 is an overall configuration diagram showing an example of an apparatus used in the welding method of the present invention.

Fig. 2 is a configuration diagram showing an example of a welding torch used in the welding method of the present invention.

Fig. 3 is a structural view showing an example of a nozzle portion used in the welding method of the present invention.

FIG. 4 is a graph showing the chemical potentials of various sulfides.

Fig. 5 is a schematic view showing a bead width and a bead height used for evaluating the appearance of a bead in the examples.

Detailed Description

Hereinafter, the mode for carrying out the present invention will be described in detail. The present invention is not limited to the embodiments described below.

The gas shielded arc welding method of the present invention is a gas shielded arc welding method for welding while feeding a consumable electrode through a welding torch and flowing a shielding gas therethrough, wherein the welding torch includes a nozzle, an inner diameter of the nozzle is 15mm or more, a nozzle-base metal distance between a tip of the nozzle and a material to be welded is 22mm or less, and a ratio (inner diameter of the nozzle/the nozzle-base metal distance) is 0.7 or more and 1.9 or less.

[ welding device ]

First, a welding apparatus that can be used in the gas metal arc welding method of the present invention will be described. The welding device is not particularly limited as long as it is a welding device for performing gas metal arc welding, and a welding device used for conventional gas metal arc welding can be used.

For example, as shown in fig. 1, the welding apparatus 1 includes: a robot 10 having a welding torch 11 attached to a tip thereof, and configured to move the welding torch 11 along a welding line of a material to be welded (hereinafter, also referred to as a "workpiece" or a "base material") W; a wire feeder (not shown) for feeding a welding wire to the welding torch 11; and a welding power supply unit 30 for supplying current to the consumable electrode through the wire supply unit and generating an arc between the consumable electrode and the material to be welded. The welding apparatus further includes a robot control unit 20 that controls the operation of a robot for moving the welding torch 11.

< welding torch >

As shown in fig. 2, the welding torch 11 automatically feeds a welding wire into a cylinder and performs arc welding using the welding wire. The welding torch 11 is equipped with a welding gun holder 12. The welding torch holder 12 fixes the welding torch 11 to the robot.

The torch barrel 21 is supported by the torch holder 12, and includes a mechanism for supporting the nozzle 71 and the contact tip body 31. The torch barrel 21 is fitted with the contact tip main body 31, and can supply the supplied welding wire to the tip of the contact tip main body 31 (the rear end of the contact tip 61) via the inner tube 22. The torch barrel 21 passes a welding current through the contact tip main body 31, and supplies a shielding gas to a space formed between the inner tube 22 and the contact tip main body 31. The contact tip body 31 includes a nozzle opening 41 and a mechanism for supporting the contact tip 61. The contact tip body 31 is made of a material having a conductive property such as metal.

The nozzle 41 is provided with a mechanism for rectifying the flow of the shielding gas. That is, the spout 41 is generally formed in a cylindrical shape, and is inserted and assembled from the distal end side of the outer periphery of the contact tip body 31. The contact tip 61 is provided with a mechanism for supplying a welding current to the welding wire and guiding the welding wire to a workpiece to be welded. Similarly, the contact tip body is also formed of a material having a conductive property such as metal for the contact tip 61.

The welding torch may be oriented vertically or obliquely with respect to the base material.

When the welding torch is tilted to the opposite side of the welding traveling direction, the angle between the perpendicular to the base material and the welding torch is called a rake angle, and when the welding torch is tilted to the welding traveling direction, the angle between the perpendicular to the base material and the welding torch is called a caster angle.

The welding torch is provided with a forward rake angle, and the protection in arc welding can be more effectively improved. In addition, the electrode is tilted backward, and the back of the weld bead can be protected, so that the oxidation reaction of the weld bead after welding can be suppressed.

In order to obtain an appropriate penetration depth and a good bead shape on the weld line, it is more preferable to perform welding in a range of-15 to 40 ° in the rake angle, that is, in a range of 40 ° in the upper limit of the rake angle and 15 ° in the upper limit of the caster angle.

< nozzle >

The nozzle 71 includes a nozzle for discharging (Ar) and carbon dioxide (CO) supplied from a gas supply device (not shown) to the base material to be welded₂) Etc. of the shielding gas. The nozzle 71 is formed in a cylindrical package, and has an internal space in which the nozzle body 31, the spout 41, and the nozzle 61 can be housed in an integrally assembled state.

The nozzle 71 has a female screw portion (not shown) formed on an inner surface of a rear end thereof for screwing the male screw portion 23 formed at the tip of the torch barrel 21. With this configuration, the nozzle 71 can block the welded portion from the atmosphere by using the shielding gas which is rectified through the nozzle 41.

(inner diameter of nozzle and nozzle-base metal distance)

Fig. 3 shows an example of the nozzle shape, and the inner diameter Do of the linear portion X in the nozzle (hereinafter, sometimes referred to simply as "linear portion") and the inner diameter D of the nozzle opening (hereinafter, sometimes referred to simply as "inner diameter of nozzle") affect the protection range and the protection performance.

The task of the shield gas in gas shielded arc welding is to shield the atmosphere from the arc, high-temperature molten metal and wire, and to prevent nitriding and oxidation of the molten portion.

Nitrogen is not usually added to the protective gas, and since the partial pressure in the protective gas is very low, it is considered that even if some air entrainment occurs, the nitrogen does not directly form a solid solution in the molten steel.

In short, it is considered that the reason why nitrogen is dissolved in molten steel is that N is introduced into the arc atmosphere due to the incorporation of nitrogen into the arc atmosphere₂The partial pressure of N is increased, and N is decomposed into N, and enters the molten steel locally heated to a high temperature by the arc.

That is, in order to suppress nitrogen in the weld metal, it is necessary to prevent nitrogen from being mixed into the arc atmosphere, and therefore, the laminar stability of the shield gas flow is important as compared with the width of the conventional shield region, and a small-diameter nozzle having a flow velocity higher and less likely to become turbulent can be used. In addition, a method of reducing the diameter is also preferable in order to enter a narrow welding position.

As a conventional method, specifically, for example, as described in patent document 2, the inner diameter of the nozzle opening is narrowed to be smaller than the inner diameter of the straight portion, and the ejected gas is sharpened to improve the directivity. In this way, conventionally, the inner diameter D of the nozzle is narrowed to improve the protection.

On the other hand, oxygen (O) causes projection of the bead shape and slag generation, but oxygen still needs to be positively added to the shield gas from the viewpoint of arc stability, and therefore the partial pressure of O in the arc atmosphere is often high. Therefore, in order to reduce the amount of oxygen in the molten metal, it is necessary to protect the entire molten pool with a protective gas, not only in the arc. As a method of protecting the same, welding may be performed while maintaining a protective gas flow in a laminar flow over a wide range.

However, if the inner diameter D of the nozzle is small as in the conventional art, the area that can be protected is small, and a wide range cannot be covered. That is, if the protection range cannot be secured widely, the weld metal after the torch passes through is exposed to the atmosphere in a state of higher temperature. Therefore, the oxidation reaction on the bead surface is promoted, and the bead shape is raised and slag is generated. Even when a predetermined amount of S is contained in a consumable electrode (wire) described later, the effect of S cannot be effectively exhibited.

Therefore, in the present invention, the inner diameter D of the nozzle is set to 15mm or more in order to widen the protection range. However, if the inner diameter of the nozzle is simply increased to secure a wide range of protection, the protective gas may be turbulent before reaching the molten metal, and the protection may be deteriorated.

Therefore, the distance between the tip of the nozzle and the material to be welded (base material) (nozzle-base material distance) is 22mm or less, and the ratio (nozzle inner diameter D/nozzle-base material distance) is 0.7 or more and 1.9 or less.

By setting the ratio of the nozzle inner diameter D, the nozzle-base material distance, and (nozzle inner diameter D/nozzle-base material distance) to the above range, a large protection range and high protection can be achieved. That is, the amount of oxygen and the amount of nitrogen in the molten metal can be kept low, and the formation of pores due to nitrogen and the projection of the bead shape due to oxygen and the increase of slag can be suppressed.

If the inner diameter D of the nozzle is less than 15mm, the protection range is narrowed, and a large amount of slag is generated by oxidation reaction of the weld metal after the torch passes. The inner diameter D of the nozzle is preferably 16mm or more, more preferably 18mm or more.

On the other hand, the upper limit of the inner diameter D of the nozzle is preferably 30mm or less, and more preferably 22mm or less. If the thickness is more than 30mm, the directivity of the gas to be ejected may be deteriorated and the protection may be deteriorated, although the thickness may be different depending on the flow rate of the protective gas. In this case, slag may be generated due to the inclusion of air, and welding defects such as pits and blowholes may be generated.

In the present invention, the relationship between the inner diameter Do of the straight portion and the inner diameter D of the nozzle opening is not particularly specified, and if the inner diameter D of the nozzle opening is 15mm or more, one of the inner diameters Do of the straight portion may be large or small, or may be the same. However, from the viewpoint of the directivity of the shielding gas, in order to improve the protection, the ratio (D/Do) of the inner diameter Do of the linear portion to the inner diameter D of the nozzle opening is preferably in the range of 0.5 to 1.0.

From the viewpoint of further obtaining the above-described effects, the nozzle-base material distance is preferably 20mm or less, and more preferably 17mm or less. More preferably 15mm or less. The lower limit of the nozzle-base metal distance is preferably 12mm or more in view of clogging of the nozzle by spatters.

From the viewpoint of further obtaining the above-described effects, the ratio (inner diameter D of the nozzle/distance between the nozzle and the base material) is preferably 1 or more, and more preferably 1.6 or less.

< protective gas >

The shielding gas used in the gas-shielded arc welding method of the present invention is not particularly limited, and Ar gas and carbon dioxide (carbon dioxide, CO) can be used₂) Oxygen (O)₂) And mixed gases thereof, and the like. Wherein N may be contained as an impurity₂、H₂And the like.

Even if 100% CO is used as the shielding gas₂The welding of (3) can also obtain the effects of suppressing the entrainment of air and preventing the oxidation reaction by the gas shielded arc welding method of the present invention. However, when Ar gas or an Ar-containing mixed gas is used as the protective gas, the oxidation reaction of the molten metal can be further reduced. Therefore, as the protective gas, Ar gas (100% Ar) or a mixed gas containing Ar is preferably used.

In the case of the Ar-containing mixed gas, the carbon dioxide content is preferably 0 to 40 vol% and the oxygen content is preferably 0 to 10 vol%. Further, it is more preferable that Ar is contained up to 92% by volume or more, the balance is at least one of carbon dioxide and oxygen, and inevitable impurities, and it is further preferable that Ar is contained up to 95% by volume or more.

Further, as inevitable impurities, N may be mentioned₂、H₂Etc., most preferably not at all (0 vol%).

The flow rate of the shielding gas is preferably 25L/min or less, and more preferably 18L/min or less, depending on the inner diameter D of the nozzle and the distance between the nozzle and the base material. This prevents the flow rate of the shielding gas from becoming excessively high, and prevents the atmosphere from being drawn into the shielding atmosphere by the high-speed gas flow.

In addition, the flow rate of the shielding gas is preferably 8L/min or more, and more preferably 10L/min or more, from the viewpoint of the pore resistance.

The ratio (flow rate) expressed by (flow rate of the shielding gas/inner diameter D of the nozzle) is preferably 0.65L/min mm or more and 1.10L/min mm or less, from the viewpoint of suppressing the air entrainment due to the high-speed gas flow. The flow rate is more preferably 0.75L/min mm or more, and still more preferably 1.00L/min mm or less.

< consumable electrode (welding wire) >

The type of the welding wire may be a solid wire, which is a steel wire, or a flux-cored wire composed of a cylindrical sheath and a flux filled inside the sheath, and does not matter. In the case of the flux-cored wire, the sheath may be of a seamless type having no seam, or may be of a seamed type having a seam. The surface of the wire (the outer side of the sheath in the case of the flux-cored wire) may or may not be plated with copper.

(S: 0.015% by mass or more)

In the welding wire of the present invention, sulfur (S) is preferably added in an appropriate amount.

S is originally an impurity element, and is preferably contained in a small amount as much as possible, like phosphorus (P). However, S in molten iron has a property of being easily adsorbed on the surface of molten iron, and has a property of reducing the surface tension. Therefore, in the present invention, this property is utilized by focusing on it, and the appropriate amount range of S in the wire is defined based on the following mechanism.

By welding the welding wire of the present invention, S atoms are selectively adsorbed on the surface of the molten pool. Here, when the protective range of the protective gas is narrow, O atoms are also adsorbed on the melt pool surface as with S atoms, and therefore, in order to cover the melt pool surface with S atoms, it is necessary to set the inner diameter D of the nozzle opening to 15mm or more as described above, so that the protective range and the protective property are improved.

The surface of the molten pool or the surface of the weld bead covered with S atoms, even if exposed to oxygen in the atmosphere, was exposed to 1/2S as shown in the chemical potential diagram of various sulfides in FIG. 4₂+O₂＝SO₂S reacts with atmospheric oxygen and SO is also formed₂(boiling point: -10 ℃ C.) to vaporize. Therefore, oxidation reaction of Fe, Mn, and the like at the time of bead surface after welding or air infiltration can be suppressed, and the bead surface after welding can be further suppressedAnd (4) generating welding slag on the surface.

It should be noted here that the reaction 2Fe + S is comparable to iron sulfide₂＝2FeS，1/2S₂+O₂＝SO₂Is more stable on the one hand, and SO₂The boiling point of (B) is-10 ℃. That is, in a wide temperature range from after welding to room temperature, the reduction reaction of FeS acts, and the oxidation reaction of Fe can be suppressed. In addition, SO is generated₂Can easily escape to the atmosphere.

Along the above mechanism, in the present invention, the surface adsorption phenomenon of S selectively acts, and in order to ensure the surface adsorption to the molten pool, the amount of S is preferably 0.015 mass% or more with respect to the total mass of the consumable electrode (wire). More preferably 0.020% by mass or more. The upper limit is preferably 0.080 mass% or less from the viewpoint of avoiding cracking of the weld metal.

Since surface adsorption of S cannot be directly observed, it is generally indirectly judged by surface tension and gas adsorption reaction. When the amount of S in the wire is less than 0.015 mass%, development of the bead shape due to surface tension is not observed, and also slag is generated, so that the oxidation suppression effect by the adsorption phenomenon of S may not be exhibited. On the other hand, if the S content in the wire is higher than 0.080 mass%, weld defects such as hot cracks may occur.

Other components and numerical ranges (component amounts) contained in the welding wire may be included, and the reason for the limitation is described below. The amount of the component is defined in a ratio to the total mass of the wire unless otherwise specified. When the welding wire is a flux-cored wire, the sum of the amounts of the sheath and the flux is expressed.

(C: 0.30% by mass or less (including 0% by mass))

The welding wire neutralizes C in the weld metal, and is effective in improving the strength of the weld metal. The amount of the spatter is not limited to a small amount, and therefore the lower limit is not set, but if the amount is large and is higher than 0.30 mass%, the spatter is bonded with a small amount of oxygen during welding to form CO gas, and bubbles are generated on the surface of the droplet, which causes spatter generation and arc instability.

When the arc is unstable, the shielding gas is disturbed, and the atmosphere is involved, which may cause a welding defect such as a blowhole and a large amount of slag. Therefore, the content of C is preferably 0.30 mass% or less. In addition, in order to secure strength, 0.01 mass% or more is preferable.

(Si: 0.20-2.50 mass%)

Si in the wire is a deoxidizing element, and is a preferable element for securing the strength and toughness of the weld metal. When the amount is small, deoxidation is insufficient, and pores may be generated, and therefore, it is preferable to contain the amount of the oxygen in an amount of 0.20 mass% or more. However, if the content is more than 2.50 mass%, a large amount of slag which is difficult to be peeled off during welding occurs, and welding defects such as slag inclusion occur. Therefore, the content of Si is preferably in the range of 0.20 to 2.50 mass%.

(Mn 0.50-3.50 mass%)

Mn in the wire exhibits an effect as a deoxidizer or a desulfurizing agent, similar to Si, and is preferable for securing the strength and toughness of the weld metal. In order to prevent the occurrence of welding defects due to insufficient deoxidation, it is preferable to contain 0.50 mass% or more. On the other hand, if the content is more than 3.50 mass%, a large amount of slag which is difficult to be peeled off during welding occurs, and welding defects such as slag inclusion occur. In addition, the strength is excessively increased, so that the toughness of the weld metal is significantly reduced. Therefore, the Mn content is preferably in the range of 0.50 to 3.50 mass%.

(P: 0.0300% by mass or less (including 0% by mass))

P is an impurity element, and the lower limit is not set, because the content is preferably as small as possible. If they are present in a large amount exceeding 0.0300% by mass, weld defects such as cracks in the weld metal may occur, and therefore, the range of 0.0300% by mass or less (including 0% by mass) is preferable.

In addition to the above elements, Ni, Cr, Mo, B, and the like are allowed to be added to the wire in appropriate amounts in accordance with the steel sheet, but these are not factors dominating the amount of slag generated.

< arc welding Condition >

(average welding Current)

When the average welding current is set to a low level, the plasma gas flow is slowed down, and the plasma gas flow can further suppress the mixing of air directly below the arc. Therefore, the average welding current is preferably 270A or less, and more preferably 250A or less.

The lower limit of the average welding current is preferably 70A or more in view of arc stability.

(pulse Current control)

The welding is preferably performed by pulse welding in which a pulse current is controlled, because the spray transition is stable and the entrainment of air due to the instability of the arc can be suppressed.

The peak current of the pulse is preferably 380A or more and 530A or less, more preferably 400A or more, and still more preferably 480A or less.

If the pulse peak current is higher than 530A, the peak current becomes too high, and the amount of the pulse peak current is slightly increased into the atmosphere in the arc. When the peak current is less than 380A, the peak current may be too low, and the amount of spatter generated may increase.

The peak time (peak width) of the pulse is preferably 0.5 to 2.0 milliseconds, more preferably 1.2 milliseconds or more, and further preferably 1.6 milliseconds or less.

If the pulse peak time is more than 2.0 msec, the peak time becomes excessively long, and the entrainment into the atmosphere in the arc may be slightly increased. If the time is less than 0.5 msec, the peak current may be too low, and the amount of spatter generated may increase.

< material to be welded (workpiece, base material) >)

The material to be welded can be a conventionally known material. For example, cold rolled steel sheets, hot rolled steel sheets, and the like can be cited.

Among these, the galvanized steel sheet is preferable because Zn vaporized by welding heat enters into the protective gas, and the oxygen partial pressure and nitrogen partial pressure of the protective atmosphere can be reduced, thereby suppressing the increase of oxygen and nitrogen in the molten metal. When the coating amount of zinc is too large, the amount of spatter generation may increase slightly, and therefore the coating amount of zinc is more preferably 20 to 120g/m²More preferably 100g/m²The following.

The welding method of the present invention can be applied if the thickness of the material to be welded is about 1.0 to 3.0 mm.

< solder >

The present invention also relates to a method for producing a welded article including a step of welding by the gas metal arc welding method, and a welded article welded by the gas metal arc welding method.

The welded object may be an automobile chassis part, and among them, a suspension arm and a suspension member are preferable.

(welding slag)

In the welded material, it is preferable that the slag having a short diameter of 5mm or more is not generated on the surface of the weld bead excluding the inner side of the arc pit portion 1mm or more from the bead seam side portion in the visually recognized slag generation state, and it is more preferable that the slag is generated intermittently than continuously when the slag is generated within 1mm from the bead seam side portion.

(splash)

The presence or absence of spatter adhering to the weld can be visually evaluated. The amount of the large spatters having a diameter of 1mm or more adhering to the weld is preferably 2 or less, and more preferably none at all.

(bead shape)

The bead shape of the welded product is preferably a ratio of the bead width α to the extra height β (bead width α/extra height β) of 3 or more in the schematic view of fig. 5, and is more preferably 5 or more in view of the paintability of the bead portion. The upper limit is not particularly limited since the smoother the bead shape is, the more preferable it is.

[ examples ] A method for producing a compound

The present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples, and can be modified and practiced within the scope conforming to the spirit of the present invention, and all of these are included in the technical scope of the present invention. The welding conditions described here are examples, and the present embodiment is not limited to the following welding conditions.

< evaluation method >

(slag formation state)

The state of the formation of dross in the weld was visually observed by a digital microscope (product of キーエンス, VHX-900). In the "slag formation state" in tables 1 to 2, "x" indicates that slag having a short diameter of 5mm or more is formed on the surface of the weld bead excluding the inner side of the arc pit portion 1mm or more from the bead seam side portion, that "o" indicates that the slag is not formed but the slag within 1mm from the bead seam side portion is continuously formed, and that "x" indicates that the slag is not formed but the slag within 1mm from the bead seam side portion is generated by fracture.

(bead appearance)

The appearance of the bead of the welded article was visually evaluated for the presence or absence of spatter adhering to the welded article and the shape of the bead. The spatter adhering to the weld was evaluated for the presence of spatter having a diameter of 1mm or more.

Regarding the bead shape, when the welding gun was set to weld perpendicularly to the material to be welded, it was evaluated whether or not the value (bead shape) indicated by (bead width/height) was 5 or less. The bead width is a range indicated by a symbol α in fig. 5, and the height is a range indicated by a symbol β in fig. 5.

"circleincircle" in "bead appearance" in tables 1 to 2 indicates that there is no spatter adhering to the weld material, the value of the bead shape is 5 or less, and ". o" is inferior in either spatter or bead shape.

< examples 1 to 45 and comparative examples 1 to 4 >

As basic conditions, a steel sheet of an SPHC material specified in JIS G3131 and an SGHC material specified in JIS G3302, each having a plate thickness of 3.2mm, was used as a base material, and flat-plate overlay welding was performed. The welding speed is 100 cm/min, and the angle of the welding gun is vertical to the base metal.

Regarding the composition of the consumable electrode (wire), in mass%, C is the same: 0.07%, Si: 0.8%, Mn: 1.5%, P: 0.010%, the content of S is shown in tables 1-2, and the balance is Fe.

The inner diameter (nozzle diameter) of the nozzle used for welding, the distance between the nozzle base metals, (inner diameter of the nozzle/distance between the nozzle and the base metal) (ratio), the flow rate of the shielding gas, (gas flow rate/nozzle inner diameter), the type of gas, the S content in the wire, the steel sheet, and the welding conditions are summarized in tables 1 to 2. The nozzle base metal distance is adjusted by adjusting the projection length of the tip projecting from the nozzle.

In the "steel sheets" in tables 1 to 2, "no plating" means untreated steel sheets on which plating is not performed. In examples 42 to 45, the base material was used in such a manner that the coating amount was 20g/m²、45g/m²、100g/m²、120g/m²The galvanized steel sheet of (1).

In addition, the peak current and the peak time (peak width) of the pulse welding performed in examples 34 to 45 are summarized in tables 1 to 2.

The above conditions, the slag formation state, and the evaluation results of the bead appearance are shown in tables 1 to 2.

[ TABLE 1]

[ TABLE 2]

From the results shown in tables 1 to 2, it was confirmed that the formation of slag having a short diameter of 5mm or more was suppressed by setting the inner diameter D of the nozzle to 15mm or more, setting the nozzle-base metal distance to 22mm or less, and setting (the inner diameter D of the nozzle/the nozzle-base metal distance) to 0.7 or more and 1.9 or less.

Further, the slag formation state can be further improved by setting the flow rate of the shielding gas to 20L/min or less, more preferably 18L/min or less, or setting the flow rate (the inner diameter D of the nozzle/the distance between the nozzle and the base metal) to 0.65 to 1.10L/min mm.

In examples 22 to 26, by setting the Ar content in the shielding gas to 92% or more, it is possible to obtain a welded product having very excellent slag formation state and bead appearance.

In examples 27 to 30, by setting the S content in the wire to 0.015 mass% or more, it is possible to obtain a welded product having an extremely excellent slag formation state and bead appearance regardless of the flow rate of the shielding gas and the Ar content.

In examples 32 and 33, by setting the average welding current to 250A or less, it was possible to obtain a welded product having an extremely excellent slag formation state and bead appearance regardless of the flow rate of the shielding gas, the Ar content, and the S content in the wire.

In examples 34 to 41, by performing pulse current control, it was possible to obtain a welded product having extremely excellent slag formation state and bead appearance regardless of the shielding gas flow rate, Ar content, S content in the wire, and average welding current.

In examples 42 to 44, the base material was coated with 20 to 100g/m²By the zinc plating treatment of the coating amount, a welded article having an extremely excellent slag formation state and bead appearance can be obtained.

The present invention has been described in detail with reference to the specific embodiments, but it is apparent to the practitioner that various changes and modifications can be made without departing from the spirit and scope of the present invention.

Also, the present application is based on japanese patent application (patent application 2015-152378) filed on 31/7/2015, which is incorporated by reference in its entirety.

[ industrial applicability ]

By preventing welding defects such as pits and blowholes caused by the inclusion of air during welding and oxidation of the bead surface, the repair work time, labor, cost, etc. for trimming the obtained welded product can be reduced.

[ notation ] to show

1 welding device

10 robot

11 welding torch

12 welding gun clamp

20 robot control part

21 welding gun barrel

22 inner pipe

23 external screw thread part

30 welding power supply unit

31 contact tip body 31

41 nozzle

61 contact tip

71 spray nozzle

Inner diameter of D-nozzle opening

Inner diameter of Do straight line part

Straight line part in X-shaped nozzle

Y weld part

W welded material (workpiece)

Width of alpha bead

Beta residual height

Claims

1. A gas shielded arc welding method for performing welding while feeding a consumable electrode through a welding torch and flowing a shield gas,

the protective gas is a mixed gas containing 92% or more of Ar and the balance of at least one of carbon dioxide and oxygen, and unavoidable impurities,

the welding torch comprises an inner tube, a contact tube body, a nozzle arranged on the periphery of the contact tube body, and a nozzle,

the mixed gas is supplied to a space formed between the inner tube and the contact tip main body, the nozzle blocks a welded portion from the atmosphere using the mixed gas rectified through the nozzle hole,

the inner diameter of the nozzle is more than 15mm,

a nozzle-base metal distance between the tip of the nozzle and the material to be welded is 22mm or less, and a ratio (inner diameter of the nozzle/the nozzle-base metal distance) is 0.7 or more and 1.9 or less,

the consumable electrode contains 0.015 mass% or more of S with respect to the total mass.

2. The gas-shielded arc welding method according to claim 1, wherein the flow rate of the shielding gas is 18L/min or less.

3. The gas-shielded arc welding method according to claim 1, wherein a ratio (flow rate of the shielding gas/inner diameter of the nozzle) is 0.65L/min mm or more and 1.10L/min mm or less.

4. The gas-shielded arc welding method according to claim 1, wherein the average welding current is 250A or less.

5. The gas-shielded arc welding method according to claim 1, wherein the pulse current control is performed such that the peak current is 380A or more and 530A or less and the peak width is 0.5 to 2.0 milliseconds.

6. The gas-shielded arc welding method according to claim 1, wherein the material to be welded is 20 to 100g/m²A coating amount of the galvanized steel sheet.

7. The gas-shielded arc welding method according to any one of claims 1 to 6, wherein the nozzle has a straight portion, and an inner diameter of the nozzle is the same as an inner diameter of the straight portion.

8. The gas-shielded arc welding method according to any one of claims 1 to 6, wherein the consumable electrode contains Si: 0.20 to 2.5 mass%, Mn: 0.50 to 3.50 mass%.

9. The gas-shielded arc welding method according to claim 7, wherein the consumable electrode contains, with respect to a total mass, Si: 0.20 to 2.5 mass%, Mn: 0.50 to 3.50 mass%.

10. A method for producing a welded article, comprising the step of welding by the gas metal arc welding method according to any one of claims 1 to 9.

11. A welded article welded by the gas-shielded arc welding method according to any one of claims 1 to 9.